Can't say that I'm a fan of this "Devil" character.
So far the story has been well told, but it certainly lives up to the grim nature of "traditional" fairy tales.
Certainly doesn't bode well for for a happy ending. Likely to be bittersweet at best. Though I will hope Cinderella and Briar get the justice they deserve. Of course, part of why the old myths and fairy tales often seemed indifferent to human suffering is because they were reflections of nature, and the human experience of living in a world governed by nature's capriciousness and the violent rule of the strong. Justice is a foreign concept to nature. It wouldn't be in the spirit of the source material to have an outcome that we would consider justice.